What to do when the builder denying penalty for invoking force major

Hi, We have brought property in whitefield. Builder have exhausted six month grace period on Dec 31st. Now since project is further delayed they are denying the 2% penalty mentioned in agreement by stating rain as major reason and invoking force major. Also all the in-person and over email negotiation and follow-up have failed. They have stopped responding to our emails. What are legal rights we have as a buyer and what are the implications?